(i) Field of the Invention
The present invention relates to a multi-phase stepping motor, and more particularly to a driving circuit for a multi-phase stepping motor in which the half-step drive operation is attained.
(ii) Description of the Related Art
Various driving means for such a multi-phase stepping motor have been proposed heretofore. U.S. Pat. No. 3,599,069, for example, discloses a multi-phase stepping motor which includes switching means each connected to windings of stators and a control circuit for controlling the switching means so that each of the windings takes any one of the three states so that the corresponding winding is excited to be one polarity or to be the other polarity or is not excited to any polarity forming a short circuit of the winding in accordance with a predetermined sequence so as to advance the motor in a predetermined direction by a predetermined step angle by means of a magnetic field produced in each of the windings. With such control means, while the circuit configuration is complicated, the dumping characteristic of the motor is maintained to satisfactory.
FIG. 9 shows another circuit configuration of drive means for the multi-phase stepping motor in which many switching elements are required but the circuit configuration is simplified. The circuit of FIG. 9 includes switching elements T1 to T10, for connecting each of starting ends and terminating ends of phase windings .phi.1 to .phi.5 of the multi-phase stepping motor to the positive pole of a D.C. power source, and switching elements T11 to T20, for connecting each of starting ends and terminating ends of phase windings .phi.1 to .phi.5 to the negative pole of the source. When half-step drive operation, for example, is performed in the circuit of FIG. 9, so-called four-phase and five-phase excitations are attained by alternately repeating one state capable of energizing four phase windings and another state capable of energizing five phase windings, each time an input pulse is supplied.
In the above prior art drive system, the circuit configuration is generally complicated and particularly if the half-step drive operation is desired in such a multi-phase stepping motor, many switching elements, for example, four times as many switching elements as the number of the phases of the motor are required. Accordingly, the circuit configuration in an output stage is also complicated and a required current capacity of the power source is four to five times or more as large as a rated current value of the windings. Further, the number of connecting wires between the motor and the driving circuit increases and hence the operation for the wire connection is complicated and troublesome. Thus, the realization of the half-step drive operation in the multi-phase stepping motor has various defects in practice.